We present a measurement of the ratio of the ¯B0s meson lifetime, in the flavor-specific decay to D+sπ−, to that of the ¯B0 meson. The pp collision data used correspond to an integrated luminosity of 1  fb−1, collected with the LHCb detector, at a center-of-mass energy of 7 TeV. Combining our measured value of 1.010±0.010±0.008 for this ratio with the known ¯B0 lifetime, we determine the flavor-specific ¯B0s lifetime to be τ(¯B0s)=1.535±0.015±0.014  ps, where the uncertainties are statistical and systematic, respectively. This is the most precise measurement to date, and is consistent with previous measurements and theoretical predictions.